The problems posed by substances which deplete the atmospheric ozone layer (ODP: ozone depletion potential) were tackled at Montreal, where a protocol was signed which imposes a reduction on the production and use of chlorofluorocarbons (CFCs). This protocol has been the subject of amendments, which have imposed the abandonment of CFCs and have extended the regulations to other products, among them hydrochlorofluorocarbons (HCFCs).
The refrigeration industry and the air conditioning industry have invested much in the replacement of these refrigerant fluids, and a product of this investment has been the commercialization of hydrofluorocarbons (HFCs).
(Hydro)chlorofluorocarbons which are used as expandants or solvents have also been replaced by HFCs.
In the automotive industry, the air-conditioning systems of vehicles which are sold in many countries have switched from a chlorofluorocarbon (CFC-12) refrigerant fluid to that of a hydrofluorocarbon (1,1,1,2-tetrafluoroethane: HFC-134a), which is less harmful to the ozone layer. However, in view of the objectives set by the Kyoto Protocol, HFC-134a (GWP=1300) is considered to have a high warming potential. The contribution to the greenhouse effect of a fluid is quantified by a criterion, the GWP (global warming potential), which indexes the warming potential by taking a reference value of 1 for carbon dioxide.
Carbon dioxide, being non-toxic, non-flammable and having a very low GWP, has been proposed as a refrigerant fluid for air-conditioning systems, as a replacement for HFC-134a. However, the use of carbon dioxide presents a number of disadvantages, associated in particular with the very high pressure of its use as a refrigerant fluid in existing apparatus and technologies.
Moreover, the mixture R-404A, composed of 44% by weight of pentafluoroethane, 52% by weight of trifluoroethane and 4% by weight of HFC-134a, is widely used as a refrigerant fluid in superstores (supermarket) and in refrigerated transport. This mixture, however, has a GWP of 3900. The mixture R-407C, composed of 52% by weight of HFC-134a, 25% by weight of pentafluoroethane and 23% by weight of difluoromethane, is used as a heat transfer fluid in air conditioning and in heat pumps. This mixture, however, has a GWP of 1800.
Document JP 4110388 describes the use of hydrofluoropropenes of formula C3HmFn, where m and n represent an integer between 1 and 5 inclusive and m+n=6, as heat transfer fluids, especially tetrafluoropropene and trifluoropropene.
Document WO 2004/037913 discloses the use of compositions comprising at least one fluoroalkene having three or four carbon atoms, more particularly pentafluoropropene and tetrafluoropropene, preferably having a GWP of not more than 150, as heat transfer fluids.
Document WO 2005/105947 teaches the addition to tetrafluoropropene, preferably 1,3,3,3-tetrafluoropropene, of a co-blowing agent such as difluoromethane, pentafluoroethane, tetrafluoroethane, difluoroethane, heptafluoropropane, hexafluoropropane, pentafluoropropane, pentafluorobutane, water or carbon dioxide.
Document WO 2006/094303 discloses an azeotropic composition containing 7.4% by weight of 2,3,3,3-tetrafluoropropene (1234yf) and 92.6% by weight of difluoromethane (HFC-32). This document likewise discloses an azeotropic composition containing 91% by weight of 2,3,3,3-tetrafluoropropene and 9% by weight of difluoroethane (HFC-152a).